New Alkaloids from the Mediterranean Sponge Hamigera hamigera

A new N-oxide benzylisoquinoline alkaloid isolated from the leaves of atemoya (Annona cherimola × Annona squamosa)

Phytochemical investigation of the atemoya aerial parts was carried out by LC-MS-IT and cytotoxic activities were evaluated as well. These results led to the identification of a new N-oxide alkaloid (dehydroanomuricine-N-oxide) and eight other alkaloids: scoulerine, reticuline, isocorydine, norisocorydine, asimilobine, nornuciferine, anonaine, and liriodenine. The new alkaloid dehydroanomuricine-N-oxide and anomuricine were also isolated. The structures of these compounds were determined by spectroscopic and spectrometric techniques. The cytotoxic capacity of crude methanolic extract and the alkaloidal fraction were evaluated, showing moderate cytotoxicity. The isolation and identification of these alkaloids are an important contribution to the chemotaxonomy of the genus Annona and the Annonaceae family.

Marine Alkylpurines: A Promising Group of Bioactive Marine Natural Products

Marine secondary metabolites with a purine motif in their structure are presented in this review. The alkylpurines are grouped according to the size of the alkyl substituents and their location on the purine ring. Aspects related to the marine source, chemical structure and biological properties are considered together with synthetic approaches towards the natural products and bioactive analogues. This review contributes to studies of structure–activity relationships for these metabolites and highlights the potential of the sea as a source of new lead compounds in diverse therapeutic fields.

Marine natural products

This review covers the literature published in 2014 for marine natural products (MNPs), with 1116 citations (753 for the period January to December 2014) referring to compounds isolated from marine microorganisms and phytoplankton, green, brown and red algae, sponges, cnidarians, bryozoans, molluscs, tunicates, echinoderms, mangroves and other intertidal plants and microorganisms. The emphasis is on new compounds (1378 in 456 papers for 2014), together with the relevant biological activities, source organisms and country of origin. Reviews, biosynthetic studies, first syntheses, and syntheses that lead to the revision of structures or stereochemistries, have been included.

Salvadenosine, a 5'-deoxy-5'-(methylthio) nucleoside from the Bahamian tunicate Didemnum sp

Salvadenosine, (1) a rare 5′-deoxy-5′-(methylthio) nucleoside, was isolated from the deep-water Bahaman tunicate Didemnum sp. The structure was solved by integrated analysis of MS and 1D and 2D NMR data. We revise the structure of the known natural product, hamiguanosinol, which is a constitutional isomer of 1, to 5 by interpretation of the spectroscopic data and comparison with synthesized nucleosides.

Bioactive dehydrotyrosyl and dehydrodopyl compounds of marine origin

The amino acid, tyrosine, and its hydroxylated product, 3,4-dihydroxyphenylalanine (dopa), plays an important role in the biogenesis of a number of potentially important bioactive molecules in marine organisms. Interestingly, several of these tyrosyl and dopa-containing compounds possess dehydro groups in their side chains. Examples span the range from simple dehydrotyrosine and dehydrodopamines to complex metabolic products, including peptides and polycyclic alkaloids. Based on structural information, these compounds can be subdivided into five categories: (a) Simple dehydrotyrosine and dehydrotyramine containing molecules; (b) simple dehydrodopa derivatives; (c) peptidyl dehydrotyrosine and dehydrodopa derivatives; (d) multiple dehydrodopa containing compounds; and (e) polycyclic condensed dehydrodopa derivatives. These molecules possess a wide range of biological activities that include (but are not limited to) antitumor activity, antibiotic activity, cytotoxicity, antioxidant activity, multidrug resistance reversal, cell division inhibition, immunomodulatory activity, HIV-integrase inhibition, anti-viral, and anti-feeding (or feeding deterrent) activity. This review summarizes the structure, distribution, possible biosynthetic origin, and biological activity, of the five categories of dehydrotyrosine and dehydrodopa containing compounds.

Amaranzoles B-F, imidazole-2-carboxy steroids from the marine sponge Phorbas amaranthus. C24-N- and C24-O-analogues from a divergent oxidative biosynthesis

Five new steroidal imidazoles, amaranzoles B-F, were isolated from extracts of the marine sponge Phorbas amaranthus along with the known amaranzole A. The C24-N-(4-p-hydroxyphenyl)imidazol-5-yl constitution found in amaranzoles A, C, and D is replaced by a C24-O-(4-p-hydroxyphenyl)imidazole-2-carboxylate motif in amaranzoles B, E, and F. The structures were elucidated by interpretation of spectroscopic data. The C24 side chain configuration was assigned by synthesis of a model ester followed by chiroptical comparisons of its CD spectrum with that of an amaranzole B derivative.

Alotaketals A and B, sesterterpenoids from the marine sponge Hamigera species that activate the cAMP cell signaling pathway

The new sesterterpenoids alotaketals A (1) and B (2) have been isolated from extracts of the marine sponge Hamigera sp. collected in Papua New Guinea. Their chemical structures were elucidated by analysis of spectroscopic data. Alotaketals A and B have the unprecedented alotane carbon skeleton, and they activate the cAMP cell signaling pathway with EC(50)'s of 18 and 240 nM, respectively.

9-(5'-Deoxy-5'-thio-β-D-xylofuranosyl)adenine Disulfide from the Southern Australian Marine Sponge Trachycladus laevispirulifer: the First Natural Occurrence of a Nucleoside Disulfide

Chemical fractionation of a southern Australian marine sponge, Trachycladus laevispirulifer, yielded 9-(5′-deoxy-5′-thio-β-d-xylofuranosyl)adenine disulfide as the first recorded natural occurrence of a nucleoside disulfide, and only the second of a xylo-nucleoside. Structure elucidation of the disulfide was achieved by detailed spectroscopic analysis and comparison to synthetic model compounds. The antibacterial, antifungal, and anticancer properties of the disulfide are documented and the literature surrounding natural and synthetic thionucleosides is reviewed.

Amaroxocanes A and B: sulfated dimeric sterols defend the Caribbean coral reef sponge Phorbas amaranthus from fish predators

Two new dimeric steroids, amaroxocanes A (1) and B (2), were isolated from Phorbas amaranthus collected on shallow coral reefs off Key Largo, Florida. The two compounds are comprised of two sulfated sterol cores bridged by an oxocane formed by different oxidative side-chain fusions. The structures were characterized by interpretation of MS and NMR spectroscopic data. The compounds are the primary components of a fraction that deters feeding of the bluehead wrasse, Thalassoma bifasciatum, in aquarium assays. When the pure compounds were assayed at eight times the natural concentration, amaroxocane B (2) was found to be an effective antifeedant, but A (1) was not.

Chemical constituents from the seeds of Trifolium alexandrinum

The ethanolic extract of the seeds of Trifolium alexandrinum afforded a new naturally occurring compound identified as methyl-alpha-glucose. The known compounds quercetin, kaempferol, apigenin 7-O-beta-D-glucoside and the nucleoside xanthosine were also isolated. The isolated compounds were identified by spectroscopic (UV, (1)H-, (13)C-NMR, DEPT, HMQC and HMBC) and spectrometric (ESI-MS/MS) analyses. The spectroscopic data of the isolated nucleoside were reported for the first time as a natural isolate.

Synthesis and biological evaluation of N-acetyl-beta-aryl-1,2-didehydroethylamines as new HIV-1 RT inhibitors in vitro

A variety of N-acetyl-beta-aryl-1,2-didehydroethylamines were synthesized by direct reduction-acetylation of beta-aryl-nitroolefins and assayed as HIV-1 non-nucleoside reverse transcriptase inhibitors (NNRTIs) for the first time. Compound 7a exhibited a TI value of >13.2 with CC50 value of >0.787 mM in C8166 cells. This structure-activity relationship (SAR) study provided a new lead for design and discovery of more potent and selective analogues act as NNRTIs.

Amorphane sesquiterpenes from a marine Streptomyces sp

The chemical investigation of the crude extract of the marine-derived Streptomyces sp. M491 yielded three new sesquiterpenes, namely, 10alpha,11-dihydroxyamorph-4-ene (4), 10alpha,15-dihydroxyamorph-4-en-3-one (6), and 5alpha,10alpha,11-trihydroxyamorphan-3-one (7). In addition, the known compounds 10alpha-hydroxyamorph-4-en-3-one (2), o-hydroxyacetanilide, genistein, prunetin, and indole-3-carbaldehyde and the macrolide antibiotic chalcomycin A were identified. The structures were determined on the basis of spectroscopic analysis, especially 1D and 2D NMR data. This is the first report of these sesquiterpenes from bacteria.

Marine natural products

This review covers the literature published in 2004 for marine natural products, with 693 citations (491 for the period January to December 2004) referring to compounds isolated from marine microorganisms and phytoplankton, green algae, brown algae, red algae, sponges, coelenterates, bryozoans, molluscs, tunicates and echinoderms. The emphasis is on new compounds (716 for 2004), together with their relevant biological activities, source organisms and country of origin. Biosynthetic studies (8), and syntheses (80), including those that lead to the revision of structures or stereochemistries, have been included.